The present invention relates to a plating process for beryllium copper and more particularly to a plating process for beryllium copper wherein a heat treating operation is needed after forming to yield a desired temper and surface quality.
Many applications exist for an electrical contact material with excellent electrical conductivity properties as well as superior spring properties. For many uses it is a further requirement that the material can be gold or other precious metal electroplated for high reliability and long life in operation. Beryllium copper is a material which has both excellent electrical conductivity and spring properties but to achieve the desired spring properties a post forming heat treatment is often necessary. However, during the heat treating of the beryllium copper, diffusion of the beryllium to the surface of the material takes place and the beryllium forms tenacious surface compounds. The abundance of the surface compounds of beryllium make the beryllium copper material very difficult to electroplate uniformly especially if a continuous automated strip plating process is desired. Typically prior art processes, if successful at all, for electroplating beryllium copper after a final heat treatment require too long a time in solution to reasonably provide for a continuous strip plating operation. Prior art processes would also have void areas in the electroplate where all the beryllium compounds were not removed or preferentially removed, or a roughen surface which would therefore make the material unusable for high reliability applications.
Accordingly, an object of the present invention is to provide an improved process for electroplating beryllium copper material.
Another object of the present invention is to provide a process for electroplating beryllium copper material which yields uniform consistent void-free plating even when a post forming heat treatment is required.
Yet another object of the present invention is to provide a process for electroplating a continuous strip of beryllium copper material even when a post forming heat treatment is required which is simple and economical and creates a uniform, void-free plated surface. Other objects and features will be in part apparent and in part pointed out hereinafter.
Briefly, the present invention involves a process particularly suitable for providing a uniform, void-free electroplated layer on the surface of beryllium copper which requires a post forming heat treatment to yield the desired hardness spring property. This process preferably involves treatment and preplating of the beryllium copper before the heat treatment in addition to possible treatment and electroplating after the heat treatment.
After final manufacturing operations are performed, the beryllium copper material is degreased and the surface and the molecular portions immediately adjacent the surface are treated to yield a copper-rich surface skin layer as set forth in co-pending application entitled "Treatment of Beryllium Copper Surface Prior to Electroplating", Ser. No. 658,320, assigned to the assignee of above application. This copper-rich surface is then activated and plated with a thin layer of nickel and then a thin layer of copper. The nickel serves as a diffusion barrier for the beryllium in the beryllium copper material as it diffuses toward the surface during subsequent heat treatment.
After the above processing steps the material is typically formed into parts blanked from the beryllium copper strip and heat treated in a conventional manner to yield the desired spring temper. The combination of the copper-rich surface which is virtually free of any beryllium and the diffusion barrier of nickel prevent the beryllium from diffusing to the surface during the heat treatment thereby providing for void-free plating. The beryllium copper material may then be treated to remove any beryllium compounds that might have formed on the edges of the surface which were exposed during forming. Then the surface of the beryllium copper material is activated for electroplating and then electroplated with preferably a precious metal plate. This process provides for void-free plated beryllium copper material of suitable temper that can be used for high reliability applications such as in electronic telephone switching equipment.